Regenerative Capacity of Ovarian Tissue 35 



8. The conclusions stated in the preceding paragraph 

 have been confirmed (Mandl, Zuckerman and Patterson, 

 1952) in a more extensive series of experiments on litter-mate 

 rats which received the following treatments : 



A. right ovary removed : more than half of left resected. 



B. right ovary removed : left ovary untreated. 



C. same as A, but remaining fragment of left ovary 



painted with tannic acid in order to destroy the 

 germinal epithelium. 



D. right ovary removed: surface of whole left ovary 



painted with tannic acid. 



Compensatory hypertrophy occurred in the ovarian tissue 

 left in the body, whether or not the germinal epithelium was 

 present, and was not associated with any increase in the 

 expected number of oocytes. At the same time a unilaterally- 

 ovariectomized animal lost fewer oocytes within a given 

 period than a normal animal possessing both ovaries. But 

 the rate of loss was substantially greater than would be 

 expected to occur in a single ovary of a normal animal, and 

 increased inversely with the amount of ovarian tissue left in 

 the body. 



The latter observation suggests that the smaller an ovarian 

 graft, the more quickly will it become depleted of its oocytes. 



9. The total number of oocytes does not increase after 

 hypophysectomy (Ingram, 1953). 



This experiment was carried out in order to test statements 

 by Swezy (1933) that stimulation by gonadotrophic hormone 

 decreases the rate of oogenesis in the adult rat, and corre- 

 spondingly, that the rate of oogenesis increases after hypophy- 

 sectomy. The hypophysectomized animals which she used 

 were, in fact, younger than her control animals, and would 

 have been expected to possess more oocytes, regardless of 

 other physiological considerations. Her data merely suggest 

 that the number of oocytes decreases more slowly with age 

 in hypophysectomized rats than in normal animals. 



These are the main observations bearing on the problem of 



